It is common to use certain types of hook-and-loop type mechanical fasteners for fixing disposable diapers, training pants and incontinence garments around a wearer. One approach is a thin, molded male fastener with low loft loop materials, preferably nonwoven, fabrics as the female components. For these uses generally low cost, soft touch, appropriate strength and increasing stretch in the waistline are important.
Hooks can be directly molded as disclosed for example in U.S. Pat. No. 5,315,740, assigned to Velcro, which discloses molded hooks with low displacement volumes so that it needs only to displace a small volume of loop fabric in order to engage therewith. The patent discloses a re-entrant hook, i.e., whose tip-portion curves over and down toward the base sheet from the upper end of the hook to define a fiber-retaining recess on the underside of the hook.
It is also known to cap molded stems on webs. Mushroom-shaped engaging projections obtained by this process are disclosed in U.S. Pat. No. 5,679,302 and U.S. Pat. No. 5,879,604 in which an extruded polymer layer is pressed against a mold with mold cavities, the cavities producing projecting stems, integral with the base. The terminal ends of the stems are then deformed with a heated pressure roller, forming the loop engaging projections. U.S. Pat. No. 6,054,091 discloses a similar method in which, however, the heated deforming surface gives an essentially lateral deformation to the stems during the deformation thereby forming re-entrant, J-shaped hooks with flat top portions. The solution of U.S. Pat. No. 6,627,133 differs from the previous ones in that the stemmed web, to be capped with a heated pressure roller, is manufactured with the method of U.S. Pat. No. 6,287,665, i.e., with a special mold constituted by a cylindrical printing screen. All documents mentioned in this paragraph are similar in that they flatten preformed stems by a hot roll.
US Patent Application 2004/0031130A1 discloses a method in which a product, comprising a polymer base and stems integral with and projecting from a base is extrusion-molded with a mold roll having a multiplicity of sophisticated mold cavities. The distal ends of the stems are then heated and melted while their feet are kept cold and solid. The melted ends are then flattened with a deforming surface. The same approach, i.e., pre-heating and successively flattening stems, appears in U.S. Pat. No. 6,592,800, U.S. Pat. No. 6,248,276 and U.S. Pat. No. 6,708,378, the latter ones also disclosing capping with a rough contact surface, creating roughened flat tops of engaging projections.
U.S. Pat. No. 6,039,911 discloses a stem-deforming apparatus comprising a long variable nip, e.g., a pair of co-operating conveyors, which gradually compressively deform the stems, unitary with the base.
U.S. Pat. No. 6,470,540 uses a hot extruded layer for deforming stems, which results in semi-spherical mushroom heads.
In U.S. Pat. No. 3,550,837 a male fastener member is described whose each engaging projection is constituted by an irregularly shaped granule with a special multifaceted surface, adhesively adhered to the base. The fastener is suitable for securing a flap of a disposable carton against opening. Engaging is provided by the granules comprising a number of tiny flat planes forming a multifaceted surface.
In U.S. Pat. No. 3,922,455 nibs of various shapes are grafted onto linear filaments, the linear filaments, protruding from a base, forming the engaging elements of a male fastener component.
In PCT publication WO 01/33989, particles are, with a scatter head of a scatter coater, randomly scattered, and fixed, onto a base. Each engaging projection is constituted by several agglomerated particles, though some individual particles may also be left present.
It was therefore an object of the present invention to provide low-cost male mechanical fasteners with advantageous properties. It was another object of the present invention to provide commercially attractive alternatives to the mechanical male fastener systems available so far and methods for making them.